1. Field of the Invention
The present invention relates to a method of manufacturing a toner, to the toner produced, and uses thereof.
2. Discussion of the Background
In recent years, demand for quality images from the market has spurred development of electrophotographic apparatuses and developing agents including toner for use therein. Toner capable of producing quality images is required to have a sharp particle size distribution. Toner particles of toner having a sharp particle size distribution behave well during development, which improves minute dot reproducibility.
Toners (chemical toner) have been developed based on suspension polymerization method or emulsification polymerization agglomeration methods in which toner particles are granulated in an aqueous phase to achieve the goal described above.
In the suspension polymerization method, toner particles are prepared from oil droplets formed by adding and stirring a monomer, a polymerization initiator, a coloring agent, a releasing agent, etc. in an aqueous phase containing a dispersion stabilizer followed by polymerization with heating. Toner particles can be reduced in size by the suspension polymerization method. However, a dispersion stabilizer is required which may degrade the chargeability due to its pressure in the remaining in toner. Without a dispersion stabilizer, a releasing agent tends to be present in the oil droplet when the oil droplet is formed so that the releasing agent cannot suitably exist on the surface of obtained toner particles.
In addition, unexamined published Japanese patent application No. (hereinafter referred to as JOP) 2004-226669 describes a method in which a releasing agent particulate covered or impregnated with a vinyl polymer by adding a polymerizable vinyl monomer and a water-soluble polymerization initiator to a releasing agent emulsion for polymerization is added when a toner component is emulsified so that a particulate releasing agent is uniformly and firmly attached to the surface of toner. However, polymerization of a releasing agent emulsion and a polymerizable vinyl monomer is required in this method. Also, the glass transition temperature (Tg) of the resin forming the particulate releasing agent is high, which degrades the releasing property at a low temperature and the low temperature fixing property.
In addition, Japanese patent No. 2663016 describes a method in which a toner is manufactured by suspension-polymerization of a material having a polar group and a polymerizable monomer containing a releasing agent in an aqueous medium so that the toner can contain a wax having a low melting point not suitably used for a toner manufactured by a pulverization method. A non-polar component such as wax is not present close to the surface of toner particles contrary to the polar component so that the toner has a pseudo-capsule structure in which the surface of the toner is covered with the polar component. However, the distribution of the wax inside the toner particle is not analyzed and thus unknown.
JOP 2002-6541 describes a toner containing a wax encapsulated therein and locally present on the surface of the toner. However, the detail of the dispersion state near the surface of the toner is not described.
JOP 2004-246345 describes the ratio of a wax exposed to the surface of a toner which is measured and determined by Fourier transform infrared attenuated total reflection (FTIR-ATR). However, toner blocking and hot-offset, and filming and paper winding are completely in a trade-off relationship. Therefore, it is difficult to improve the fixing property furthermore by improvement of toner or control of the average dispersion diameter of wax.
A chemical toner can be manufactured by emulsifying a liquid phase of toner components comprising at least a resin and a coloring agent dissolved or dispersed in an organic solvent, or a liquid phase of a toner composition comprising a coloring agent dissolved or dispersed in a liquid monomer in an aqueous medium.
The volume average particle diameter (Dv value) of the toner provided by this method is smaller than the toner provided by pulverization and has a uniform particle diameter with a sharp particle diameter distribution. That means Dv/Dn value is close to 1.00 (Dn means number average of particle diameter).
The toner that satisfies these characteristics provides a high-resolution picture without picture defects or offsets, because particle diameter of the toner is uniform, so each toner also has uniform properties including amount of charge of each toner and a speed for fusion of each toner. As thus described, for providing high-resolution and high durability, a toner that satisfies a uniform particle diameter with a sharp particle diameter distribution, namely a toner where Dv/Dn is small, is needed.
A chemical toner is suitable for manufacturing a uniform particle diameter having a sharp particle diameter distribution as compared to a toner prepared by pulverization. But when an emulsification condition during emulsification process is not appropriate, chemical toner that satisfies a uniform particle diameter with a sharp particle diameter distribution can't be provided. During the emulsification process, continuous emulsification facilities can be used.
JOP H09-311502 describes a technology using a mechanical shearing force as a continuous emulsification technology. JOP H09-311502 discloses a continuous mechanism, but the number of times of passing by the emulsifier or dispersion machine is only once for the disclosed continuous mechanism. The emulsifier or dispersion machine disclosed in JOP H09-311502 has turn teeth of plural steps. However, it doesn't always provide an ideal mixing ratio of a melting complex including a colorant as well as a resin and an aqueous medium on the spot where a mixture begin to be received a shearing force of the shear teeth.
Under such condition, even if the shearing force was continually as well as multiple times added, the toner particle diameter after an emulsification considerably varies as long as the mixing ratio of a melting complex including a colorant as well as a resin and an aqueous medium varies depending on the spot. It is important to repeat micro dispersion and macro mixture to emulsify a melting complex including a colorant and a resin together with an aqueous medium.
For a method based on this way of thinking, there is a known batch type emulsification method. A melting complex including a colorant and a resin together with an aqueous medium are emulsified in a tank being situated in an emulsifier by the method.
By this batch-style method, macro mixture by liquid circulation in a tank is made to grapple with an emulsifier or micro dispersion by dispersion machine. However, there is a problem not to be able to secure enough productivity.